The most common and most likely answer to this crossword clue is the 9 letter word EMANATION
I've seen this crossword clue in The Guardian
E
M
A
N
A
T
I
O
N
More clues leading to the result EMANATION
- Discharge from English mother country
- Call up process to cut carbon emission
- Discharge English soldier that’s hit volunteers from the south
- Pouring out tea in Oman sloppily
- Setter reversed a state that’s flow
- Issue half of them before a race
- Issue beginning to engage mother country
- Discharge from English graduate society
- What comes out from English master meeting people
- Coming out from a setter overland
Buddy explains!

The straight part
We know that "flow" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case flow = emanation.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does EMANATION mean?
EMANATION noun- The act of flowing or proceeding (of something, quality, or feeling) from a source or origin.
- That which issues, flows, or proceeds from any object as a source; efflux; an effluence.
- The element radon.
- The generation of the Son and the procession of the Holy Spirit, as distinct from the origination of created beings.